The present invention relates to a servo pattern formed in a recording medium of a data storage device and, more particularly to formation of a servo pattern by self-servo writing and a method for reading/writing data from/in the recording medium having the servo pattern.
In the data storage device in which the recording medium is scanned by a head and magnetic or optical means is used to read/write data from/in the recording medium, as means for increasing a recording density, servo writing is carried out to write a servo pattern used for positioning the head in the recording medium.
In a data storage device such as a hard disk device which uses a disk-like recording medium, tracks for recording data are concentrically set. Conventionally, in servo writing in the hard disk device, because of limitations or the like in a manufacturing process, a servo pattern has been written by a fixed track pitch.
However, in data writing by a head, a writing width varies in each product head. Thus, in the case of writing the servo pattern by a fixed track pitch, a track pitch must be decided on the assumption that a head of a large writing width is used. This is because of a possibility that if a track pitch is narrow with respect to a writing width of a head, data may be overwritten in an adjacent track during data writing to erase original data written therein.
As described above, servo patterns written in the disk-like recording medium (referred to as disk, hereinafter) are written at sufficient intervals by considering variance in writing width among the individual heads. As a result, waste spaces are generated in the data storage device having a head of a small writing width.
On the other hand, as means of replacing the conventional servo writing for writing the servo pattern in the disk by the fixed track pitch, a method is conceivable which uses a self-servo writing for executing servo writing by a head itself for reading/writing data from/in the disk to individually write servo patterns by a track pitch consistent with head characteristics. According to this method, since the servo writing can be carried out in accordance with the head characteristics (writing width, and reading width) of each product, it is possible to obtain a good servo pattern optimized for servo control of each product.
However, if the method for individually writing the servo patterns in the disk by the self-servo writing is utilized, since track pitches are individually set for the respective products, a problem is consequently created that to execute accurate seeking control, information regarding a track pitch (track per inch (TPI) information) intrinsic to each disk must be known beforehand.
A conceivable means for saving the TPI information intrinsic to the disk, for example, is writing of the TPI information as data in a data area of the disk itself. However, a seeking operation is executed with the TPI unknown until the head reaches an address in which the TPI information has been written. Consequently, an accurate operation cannot be expected.
Furthermore, as another means for saving the TPI information intrinsic to the disk, storage means such as an electrically erasable and programmable ROM (EEP-ROM) may be provided to save the information. However, in the manufacturing process of a general hard disk device, since a control card loading an EEP-ROM and a disk are separately manufactured, in order to save TPI information intrinsic to the disk in the EEP-ROM, management must be executed as to which control card and which disk in a product are combined, and the TPI information must be recorded in the EEP-ROM after the control card and the disk are loaded on the hard disk device. Consequently, the manufacturing process becomes complex.